Heatsink compound is a substance used in the installation of heatsinks, usually on a central processing unit (CPU) or similar computer device, to assist in effective heat transfer. A number of different substances can be used in making such compounds, though ceramic materials such as zinc oxide and beryllium oxide are quite common, as are metallic substances like silver and aluminum. Carbon fibers and even diamond powder can also be used in making these compounds, and though quite effective, such formulas are also significantly more expensive than the other types. Heatsink compound may not always be necessary for heatsink installation, as some heatsinks come with similar products already applied by the manufacturer.
Sometimes also called thermal grease or thermal compound, heatsink compound is created to increase effective heat transfer between a device such as a CPU and the heatsink connected to the device. A heatsink is usually designed with a flat surface intended to come into contact with the CPU or similar device. During standard usage of a computer, the CPU and other components can produce a great deal of heat, which can cause problems for the computer including hardware damage. In order to alleviate this heat buildup, heat is transferred by physical contact from the CPU into the heatsink, where it is then distributed into the air and fans move the heat out of the computer.
While the flat surface on a heatsink and the CPU may seem to come into perfect contact, microscopic flaws and pits on each surface can actually greatly reduce how well they contact each other. Heatsink compound is applied to the surface of the heatsink to fill in these gaps and make a more effective connection between the two surfaces. By using materials such as ceramic powders, like beryllium oxide, this is made even more effective.
This is because ceramic materials transfer heat even more effectively than air, so the heat transfer is not only made more thorough but uses materials that are more conductive. Heatsink compound made using metallic substances like silver can work even better than ceramic, but typically cost more. Carbonaceous materials like diamond dust and carbon fiber are usually the most effective but are also often the most expensive. Whichever conductor is used, it is typically suspended in a semi-fluid base similar to a gel or viscous oil. Silicone grease is usually used as the base, though mineral oils can also be used as a medium in heatsink compound.